Speed/Connection Issue with Large Number of Torrents (1300+)

[Drew Pickles]

I've been using Deluge for a few years with no issue and absolutely love it! I've recently added a large number of torrents that are currently seeding (1278 seeding, with an additional 5 downloading (+29 queued) at this time). I've had great speed results up until I hit around approximately 700 torrents. At this point it will not perform any downloads for a long amount of time, or show seeding activity (12 hours+) then have a burst of activity where normal downloading speeds occur. However it still seems to be announcing these torrents to trackers (UI on multiple tracker logins show that I am seeding them).

I suspect that this is an issue with my preferences and would like some guidance on improving them, they are listed below (I believe a lot of them are still their default values from installation):

• Global Bandwidth Usage
  - Maximum Connections: -1
  - Maximum Upload Slots: 4
  - Maximum Download Speed (KiB/s): -1.0
  - Maximum Upload Speed (KiB/s): -1.0
  - Maximum Half-Open Connections: 100 (Is this the culprit?)
  - Maximum Connection Attempts per Second: 20
  - Ignore limits on local network: True
  - Rate limit IP overhead: True
  Per Torrent Bandwidth Usage
  - Maximum Connections: -1
  - Maximum Upload Slots: -1
  - Maximum Download SPeed (KiB/s): -1.0
  - Maximum Upload Speed (KiB/s): -1.0
  Active Torrents
  - Total active: 2000 (I've just bumped this way up to accommodate future additions)
  - Total active downloading: 5
  - Total active seeding: 2000
  - Do not count slow torrents: True

• OS Information
  - Debian 7.8
  - Deluge 1.3.3
  - libtorrent 0.15.10.0

Thank you for your help in advance!